Coater with margin control means



ire States The instant invention relates to a device for coating atraveling sheet, and more particularly, to margin control means for adevice for coating a paper web.

Although the instant invention may have application in a number offields, including the coating of a number of different types oftraveling sheets in the form of fabrics or cloth as well as paper, theinstant invention is particu larly useful in the coating of paper andwill be described primarily in connection therewith. In the ordinarypaper coater, the web travels over a back-up drum and a layer of coatingis ordinarily applied by a first means, followed by a second means forsmoothing or more uniformly applying the coating to the web. Such secondmeans may be in the form of a doctor roll or blade. A difficultyencountered, however, is that the doctor means will actually spread thecoating beyond the marginal edge of the web and onto the surface of theback-up drum. This leads to undesirable operating conditions. Also, theapplicator means may apply coating to the drum surface beyond themarginal edges of the web. In either case, the coating on the drumsurface must be removed before it completes one revolution, or it maylead to sticking of the underside of the web to the drum or similardifficulties.

The instant invention affords a deceptively simple and uniquearrangement for avoiding these difficulties. In the instant arrangementan applicator roll is employed to apply coating to the web on the drum,but this applicator roll applies coating only to the main body of theweb and not to relatively thin marginal edge portions of the web. Theapplicator roll is provided with wiper means which extend inwardly fromthe opposite edges or ends of the roll a controlled distance. In thisway, the film of coating material picked up by the applicator roll isremoved at the ends of the applicator roll so that no coating is appliedto the marginal edges of the traveling sheet. It is then possible to usea simple trailing blade or doctor blade at the off-running side of thenip between the drum and the applicator roll for smoothing the coatingmaterial on the web. No side dams need be mounted with the blade toprevent flow of coating material laterally onto the drum. Instead, theadjustable wipers are mounted in association with the applicator roll soas to compensate for any spreading of the coating material laterally atthe trailing blade. Also, the applicator roll speed is controlled sothat an amount of coating material is applied to the web that will notspread appreciably at the trailing blade. It will be appreciated thatthe slight spread, if any, in the coating material at the blade willdepend upon the characteristics of the coating material, thecharacteristics of the blade and the speed of operation, although theamount of spread will remain substantially constant for a given set ofoperating conditions. Under these circumstances the wipers areadjustably mounted in precisely the position desired to compensate forthe other operating factors.

It is, therefore, an important object of the instant invention toprovide an improved coating device.

Another object of the instant invention is to provide an improved devicefor coating a traveling sheet which comprises a back-up roll wrapped bythe traveling sheet, an applicator roll picking up coating material andapplying it to the sheet on said back-up roll, blade means smoothing theapplied coating material on the sheet, and wiper means extendinginwardly from opposite ends of the applicator roll to wipe the ends freefrom coating material and thereby prevent the application of coatingmaterial to marginal edges of the traveling sheet.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

FIGURE 1 is an essentially diagrammatic side elevational view of acoating device of the instant invention; and

FIGURE 2 is an elevational view taken from the left hand side of FIGURE1, with parts broken away.

As shown on the drawings:

The coating device of the instant invention, indicated generally by thereference numeral 1%, comprises a back up roll or drum 11 which iswrapped by a traveling sheet or web 12, an applicator roll 13 picking upcoating material M and applying it to the sheet 12 on the back-up roll11, blade means 14 smoothing the applied coating material M on the sheet12, and wiper means 15, 15 extending inwardly (FIGURE 2) from oppositeends of the applicator roll 13 to wipe the ends free from coatingmaterial M and thereby prevent the application of coating material tomarginal edges of the traveling sheet 12.

The rotary drum or back-up roll 11 is driven by suitable drive meanssuch as a motor indicated diagrammatically at 16, so as to attain apredetermined surface speed on the'drum 11. The drum 11 receives the web12 on the surface thereof for travel at the surface speed of the drum11. As indicated in FIGURE 2, the drum 11 is of greater length (ortransverse dimension with respect to the web 12) than the web 12, so asto assure that the web 12 is backed by the drum 11 throughout its entirewidth. This leaves exposed edges 11a, 11a of the drum surface and theinstant invention provides means for avoiding the application of coatingmaterial M to these exposed drum edges 11a, 110. In fact, the instantinvention provides means for leaving a slight marginal edge 12a, 12a ofthe web 12 uncoated.

The applicator roll 13 is also driven by a suitable drive means such asa motor indicated diagrammatically at 17 and the applicator roll 13 hassubstantially the same length as the drum 11. The applicator roll isrotated, however, at a direction opposite to the direction of web traveland the direction of rotation of the drum 11 at a nip N'formed betweenthe drum 11 and the applicator roll 13. The nip N is not a press nip andit merely permits contact between the web 12 and the applicator roll 13to the extent necessary to apply the coating material M at the nip N.The extent of contact between the applicator roll 13 and the web 12 andthe relative speeds are correlated so that the web 12 removes coatingmaterial from the surface of the applicator roll 13 slightly morerapidly than the coating material is brought to the nip N with theresult that the coating material M is spread much more thinly on the web12 than on the surface of the applicator roll 13. As will be seen, theapplicator roll 13 is partially immersed in a bath 18 of coatingmaterial M and the amount of coating material M that is filmed onto theuprunning side of the applicator roll 13 is relatively difficult tocontrol. Variations in the level of coating material M in the bath 18'will make appreciable differences in the amount of coating material Mapplied by the applicator roll 13. These conditions can be controlled,however, so that the desired amount of coating material M is applied tothe web 12; and as has been pointed out, this amount is much less perunit of area on Patented Apr. 17, 1962 the web than the amount ofcoating material per unit of area on the applicator roll surface.

The function of the trailing blade 14 is thus essentially that ofsmoothing the coating material, rather than actual removal of excess. Ifremoval of excess coating material M occurs deliberately oraccidentally, you will note that the trailing blade 14 is also mountedover the bath 18 so that the coating material M can return to the bath18. The trailing blade 14 is formed of a mounting bar 14a which holds athin blade 14b in close running relation to the drum 11 (and the coatedweb 12 thereon) at the offrunning side of the nip N. The blade 14bextends the full length of the roll 11, or substantially so, so as tosmooth coating across the full width of the web 12.

It will be appreciated that, even though smoothing is the primaryfunction of the blade 14b, there may be a slight spreading or lateraloutward movement of the coating material M on the web 12. This slightspreading will be substantially uniform for any given set of operatingconditions, but the trailing blade is not provided with end dams or thelike to restrain a pool of coating material. A slight spreading takesplace and then the coating material may drop down from the blade intothe bath 18. If the web 12 is coated across its entire width, it will beappreciated that however slight the spreading may be it will result inthe application of coating material to the surface of the drum 11.

In the practice of the instant invention edge wipers 15, 15 are mountedin association with the applicator roll to wipe the uprunning edgesthereof. As shown in FIG- URE 2, the edge wipers 15, 15 are mounted forthreaded engagement with frame elements 19, 19 to permit limited axialadjustment thereof. The bath 18 applies coating material M to theunderside of the applicator roll 13 for travel on the uprunning side ofthe nip N. The edge wipers 15, 15 are interposed between the bath 18 andthe nip N on the uprunning side of the applicator roll 13. The wipers15, 15 may be formed of suitably durable resilient material such asrubber or the like synthetic elastomers and the wipers 15, 15 are urgedagainst the end portions 13a, 13a of the applicator roll 13 so as towipe the end portions 13a, 13a clean. The sheet 12 in FIGURE 2 is shownas having a predetermined substantially uniform transverse dimension B.The wipers 15, 15 are spaced apart a distance C which is less than theweb transverse dimension B. The wipers 15, 15 permit the application ofcoating material to the web 12 only across a transverse dimension C,which is substantially the space between the wipers 15, 15. This leavesan uncoated marginal edge 12a, 12a on both sides of the web 12. Asindicated in FIGURE 2, the blade 14b (shown fragmentarily) smooths thecoating material on the web 12 and results in a very slight spreading ofthe coating on the web 12 to obtain a coating having a lateral dimensionA, slightly greater than the initial lateral dimension C of the coating,but still less than the lateral or transverse dimension of the web B.

The wipers 15, 15, in association with the applicator roll 13, thuspermit the use of a simplified trailing blade arrangement 14 which isparticularly effective for smoothing the coating to the desired extent.

The device also permits starting a new web without the diiiiculties ofapplying a pool of coating before stable speed is reached and alsoavoids most of the ditticulties encountered when the web breaks. Forexample, if during a start-up of the machine, an applicator roll willtend to apply too much coating to the web (so that spreading isexcessive at the blade 14b), the adjustable wipers 15, may be movedinwardly an appreciable distance to compensate for this spreading. Asmachine speeds are reached, the adjustable wipers can be moved back tothe desired position, without in any way interfering with the operationof the machine.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

We claim as our invention:

1. In a device for coating a traveling paper web having a predeterminedsubstantially uniform transverse dimension, in combination, a rotarydrum of greater length than said dimension receiving a paper web on thesurface thereof and rotating at a predetermined surface speed, a rotaryapplicator roll of substantially the same length as the drum mounted innip-defining relation to the drum for receiving the paper webtherebetween, means rotating the roll at a direction opposite therotation of the drum at the nip and at a surface speed slower than thatof the drum, a source of paper coating material feeding coating onto theroll for application to the paper Web at the nip, a trailing doctorblade extending at an angle in the direction of travel of the web as itleaves the blade at the off-running side of the nip extendingsubstantially the full length of the drum in close running relationtherewith to smooth paper coating material on the web traveling on thedrum, and adjustably mounted end wipers spaced apart less than saidpaper web transverse dimension, said end wipers extending inwardly fromopposite ends of the applicator roll to wipe the ends free from papercoating material and thereby prevent the application of coating materialto marginal edges of the traveling sheet.

2. A device for applying a paper coating to a traveling paper webcomprising a back-up roll wrapped by a traveling paper web, means fordriving said roll in rotation at a first peripheral speed, a containerfor a pool of coating material positioned beneath the back-up roll, anapplicator roll having its lower circumferential portion submerged inthe pool picking up paper coating material and positioned to form acoating nip with the back-up roll for applying coating to the paper webon said back-up roll, means for driving said applicator roll at a secondperipheral speed slower than said first speed, a thin doctor bladeextending in the direction of paper travel to be in a trailing positionand positioned after said nip and above the container to be inengagement with the paper web on the back-up roll smoothing the appliedpaper coating material on the paper web with excess coating materialrunning downwardly into the container, wiper blades extending axiallyinwardly from opposite ends of the applicator roll from the edge thereofto project inwardly a short distance beyond the axial location of theedges of the paper web to wipe the ends of the applicator roll free fromthe paper coating material and thereby prevent the application of papercoating material to the marginal edges of the traveling paper web, thewiped material dropping downwardly into the container, said wiper bladesextending axially beyond the edge of the roll and outwardly thereof forguiding liquid coating to drip down into the container, and anadjustable support mounted on the container and connected to each ofsaid wiper blades for adjusting the axial position at each end of theapplicator roll to accurately control the width of the paper coatingmaterial applied to the applicator roll relative to the width of thetraveling paper edge and thereby control the width of uncoated paper atthe edge of the web.

References Cited in the file of this patent UNITED STATES PATENTS856,224 Clingman June 11, 1907 1,218,419 Labornbarde Mar. 6, 19171,493,029 Frye May 6, 1924 1,968,911 Potdevin Aug. 7, 1934 2,352,658Richmond et al. July 4, 1944 2,525,920 Mackey Oct. 17, 1950 2,534,320Taylor Dec. 19, 1950 2,563,544 Moore et a1. Aug. 7, 1951 2,681,636Fridolph June 22, 1954 2,855,894 White et a1 Oct. 14, 1958

